58 THE DEVELOPMENT OF THE SALIVARY GLANDS IN MAN 



obliterated, to appear again in the lingual region for a distance of 120 fi, 

 extending into the cranial half of the reniform segment of the 

 duct. 



At the orifice the lumen is reduced to a slit with its walls in contact. 

 The wall of the duct is composed of two or three rows of cuboidal 

 elements. Next the lumen there is a well-defined single layer of 

 squamous cells. On the right side the greater sublingual is absent. 

 The lumen extends from the orifice for a distance of 150 fi. The duct 

 shows the same arrangement of its cells as that of the opposite side. 

 A reniform segment was not observed. 



15. Chievitz. Embryo of 10 weeks. Right side dissected. Left 

 side cut into serial sections. On the left the orifice of the subma.xil- 

 lary is situated 360 fJ- caudal to the frenulum, in a parietal position. 

 The orifice is continued craniad b}' a \'ery faint sulcus, the fundus of 

 which shows no epithelial thickening. The alveolar sulcus (laterale 

 Rinne) is widely separated from the lingual sulcus. From its fundus 

 a crest projects ventrad and mesad. A few short rounded sprouts 

 are attached to this crest. Farther craniad a small plug is attached 

 to the floor of the alveolingual gutter between, and without 

 relation to. its sulci. A similar sprout is attached to the lateral wall 

 of the lingual sulcus (also present on the right). The lumen of the 

 subma.xillary duct extends into some of its penultimate divisions. 



16. Hammar. Embryo of 24.4 millimeters length. Near the 

 orifice of the subma.xillary duct are fi\'e small sprouts, which arise 

 from the lateral wall of the alveolingual region somewhat assymetrically. 

 For these elements there is no special epithelial ridge. 



17. Bujard. Embryo of about 10 weeks. Total length 5 centi- 

 meters. The submaxillary has attained an advanced stage of develop- 

 ment. Its duct opens craniad of the fremdum close to the median 

 fine ; its pro.ximal portion is vertical to the epitheHum of the mouth 

 for a short distance, then, turning abruptly, it is directed horizontally 

 caudad parallel to the floor of the alveolingual gutter, eventually 

 bending ventrolaterad to join the body of the gland. Here it divides 

 into three principal trunks. Just before undergoing this di\nsion 

 the duct gives off a ventral branch, which supplies an accessory sub- 

 ma.xillary lobule, the relation of which to the mylohyoid is not given. 

 A lumen is present as far as the terminal sprouts. In the submaxiUary 



